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United States Patent |
6,252,235
|
Niino
,   et al.
|
June 26, 2001
|
Apparatus for imaging fluorescent particles
Abstract
An apparatus for imaging fluorescent particles comprises an imaging vessel
having a lower section defining an interior space for containing
fluorescent particles, the lower section having a side wall, a bottom wall
and an exterior surface portion defining an entry surface for transmitting
into the interior space a flat excitation beam of light. A light
projecting device projects a flat excitation beam of light onto the entry
surface of the imaging vessel in a direction generally parallel to the
bottom wall thereof to illuminate the fluorescent particles. Images of the
illuminated fluorescent particles are captured from the bottom wall of the
imaging vessel.
Inventors:
|
Niino; Masao (Gamagori, JP);
Matsui; Hiroki (Gamagori, JP);
Komatsu; Akio (Gamagori, JP)
|
Assignee:
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Kowa Company Ltd. (JP)
|
Appl. No.:
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213763 |
Filed:
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December 17, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
250/458.1; 250/227.22; 250/459.1 |
Intern'l Class: |
G01N 021/01 |
Field of Search: |
250/458.1,459.1,227.22
|
References Cited
U.S. Patent Documents
Re32598 | Feb., 1988 | White | 356/301.
|
5225164 | Jul., 1993 | Astle | 356/440.
|
5355215 | Oct., 1994 | Schroeder et al. | 356/317.
|
5424841 | Jun., 1995 | Van Gelder et al. | 250/458.
|
5428451 | Jun., 1995 | Lea et al. | 250/458.
|
5436717 | Jul., 1995 | Ogino | 250/458.
|
5457527 | Oct., 1995 | Manns et al. | 356/246.
|
6071748 | Jun., 2000 | Modlin et al. | 250/459.
|
6097025 | Aug., 2000 | Modlin et al. | 250/227.
|
Primary Examiner: Hannaher; Constantine
Assistant Examiner: Gabor; Otilia
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. An apparatus for imaging fluorescent particles stained with a
fluorescent dye, comprising:
an imaging vessel having an interior space, an exterior surface, an upper
portion, and a bottom portion having a side wall and a bottom wall for
collecting fluorescent particles, a part of the exterior surface of the
imaging vessel corresponding to the bottom portion defining an entry
surface of the imaging vessel for receiving a flat excitation beam of
light;
light generating means for generating a flat excitation beam of light for
exciting the fluorescent particles collected in the bottom portion of the
imaging vessel;
light projecting means for projecting the flat excitation beam of light
generated by the light generating means onto the entry surface of the
imaging vessel in a direction generally parallel to the bottom wall
thereof to illuminate the fluorescent particles collected in the bottom
portion of the imaging vessel; and
means for capturing images of the illuminated fluorescent particles from
the bottom wall of the imaging vessel.
2. An apparatus according to claim 1; further comprising a shielding member
for covering exterior surface portions of the imaging vessel other than
exterior surface portions thereof corresponding to the bottom portion.
3. An apparatus according to claim 1; further comprising a mask having a
slit-shaped aperture; and wherein the light projecting means includes
means for projecting the flat excitation beam of light through the
slit-shaped aperture to illuminate only exterior surface portions of the
imaging vessel in a vicinity of the bottom portion thereof.
4. An apparatus according to claim 1; wherein the light generating means
includes a cylindrical lens for forming excitation light into the flat
excitation beam of light; and wherein the light projecting means includes
means for projecting the flat excitation beam of light to illuminate only
exterior surface portions of the imaging vessel in a vicinity of the
bottom portion thereof.
5. An apparatus according to claim 1; wherein the light projecting means
includes scanning means for scanning the flat excitation beam of light
along exterior surface portions of the imaging vessel in a vicinity of the
bottom portion thereof.
6. An apparatus according to claim 1; wherein the light projecting means
include a bundle of optical fibers having an exit end arranged in a
straight line for illuminating only exterior surface portions of the
imaging vessel in a vicinity of the bottom portion thereof.
7. An apparatus according to claim 1; wherein the light projecting means
include an optical element for uniformly illuminating exterior surface
portions of the imaging vessel in a vicinity of the bottom portion
thereof.
8. An apparatus according to claim 7; wherein the optical element comprises
is a diffusion plate.
9. An apparatus according to claim 1; wherein the bottom portion of the
imaging vessel has side surfaces part of which define the entry surface of
the imaging vessel.
10. An apparatus according to claim 9; wherein the bottom portion of the
imaging vessel is generally square-shaped in cross-section and one side
thereof forms the entry surface of the imaging vessel.
11. An apparatus according to claim 9; wherein the bottom portion of the
imaging vessel has a generally round-shaped cross-section; and wherein the
light projecting means includes a negative cylindrical lens disposed on a
side of the entry surface of the imaging vessel.
12. An apparatus according to claim 9; wherein the bottom portion of the
imaging vessel is generally rectangular-shaped in cross-section and one
side thereof forms the entry surface of the imaging vessel.
13. An apparatus for imaging fluorescent particles comprising:
an imaging vessel having a lower section defining an interior space for
containing fluorescent particles, the lower section having a side wall, a
bottom wall and an exterior surface portion defining an entry surface for
transmitting into the interior space a flat excitation beam of light;
light projecting means for projecting a flat excitation beam of light onto
the entry surface of the imaging vessel in a direction generally parallel
to the bottom wall thereof to illuminate the fluorescent particles; and
means for capturing images of the illuminated fluorescent particles from
the bottom wall of the imaging vessel.
14. An apparatus according to claim 13; further comprising a shielding
member for covering exterior surface portions of the imaging vessel other
than the exterior surface portion of the lower section.
15. An apparatus according to claim 13; further comprising a mask having a
slit-shaped aperture; and wherein the light projecting means includes
means for projecting the flat excitation beam of light through the
slit-shaped aperture to illuminate only the exterior surface portion of
the lower section of the imaging vessel.
16. An apparatus according to claim 13; further comprising light generating
means for generating excitation light, the light generating means having a
cylindrical lens for forming the excitation light into a flat excitation
beam of light; and wherein the light projecting means includes means for
projecting the flat excitation beam of light formed by the cylindrical
lens to illuminate only the exterior surface portion of the lower section
of the imaging vessel.
17. An apparatus according to claim 13; wherein the light projecting means
includes scanning means for scanning the flat excitation beam of light
along the exterior surface portion of the lower section of the imaging
vessel.
18. An apparatus according to claim 13; wherein the light projecting means
include a bundle of optical fibers having an exit end arranged in a
straight line for illuminating only the exterior surface portion of the
lower section of the imaging vessel.
19. An apparatus according to claim 13; wherein the light projecting means
include an optical element for uniformly illuminating the exterior surface
portion of the lower section of the imaging vessel.
20. An apparatus according to claim 19; wherein the optical element
comprises is a diffusion plate.
21. An apparatus according to claim 13; wherein the lower section of the
imaging vessel is generally square-shaped in cross-section and one side
thereof forms the entry surface for transmitting the flat excitation beam
of light into the interior space.
22. An apparatus according to claim 13; wherein the lower section of the
imaging vessel is generally rectangular-shaped in cross-section and one
side thereof forms the entry surface for transmitting the flat excitation
beam of light into the interior space.
23. An apparatus according to claim 13; wherein the lower section of the
imaging vessel has a generally round shaped cross-section; and wherein the
light projecting means includes a negative cylindrical lens disposed on a
side of the entry surface of the imaging vessel.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for imaging fluorescent particles,
and more particularly to an apparatus for imaging fluorescent particles
such as leukocytes or the like stained with a fluorescent dye.
2. Description of the Prior Art
In the medical field, platelet preparations and erythrocyte preparations
are produced by extracting platelets and erythrocytes from whole blood.
These platelet and erythrocyte preparations are each used for blood
transfusions, and it is undesirable for either preparation to contain
leukocytes. It is therefore important to be able to know how many
leukocytes the preparations contain. Conventionally this is done by
placing a sample platelet preparation in a NAGEOTTE chamber, staining with
a fluorescent dye, projecting an excitation light onto the sample and
counting leukocytes via a microscope. Specifically, a 50 microliter sample
is taken from a 200 or 400 milliliter bag of platelet preparation, the
leukocytes in the sample are counted and converted to a leukocytes count
for the whole bag. This is a tiring, inefficient, time-consuming task that
has to be done by skilled personnel.
An apparatus has been proposed to enable leukocytes to be counted, instead,
by staining the leukocytes with a fluorescent dye, illuminating the sample
with an excitation light having predetermined wavelengths, using a CCD
camera or the like to image the sample and then analyzing the images to
obtain a count of the leukocytes. However, the solution containing the
stained leukocytes also contains fluorescent dye that also emits
fluorescent light. Thus, since not only the stained leukocytes but also
the fluorescent dye itself is excited by the excitation light, there is a
marked decrease in the contrast of the leukocytes that it is desired to
observe or image. In some cases, the contrast may worsen to the point that
the leukocyte images become so buried in the background that they cannot
be picked out, making it impossible to count the leukocytes.
An object of the present invention is to provide an apparatus for imaging
fluorescent particles that enables the fluorescent particles to be well
imaged by reducing the effect of background light.
SUMMARY OF THE INVENTION
To attain the above object, the present invention provides an apparatus for
imaging fluorescent particles stained with a fluorescent dye, comprising
an imaging vessel for collecting and accommodating the fluorescent
particles in a bottom portion thereof, means for generating an excitation
light for exciting the fluorescent particles, illumination means for
illuminating only a vicinity of the bottom portion of the imaging vessel
by the excitation light, and means for obtaining images from below the
bottom portion of the imaging vessel.
In accordance with this arrangement, as the fluorescent particles that are
the object of interest are accumulated in the bottom part of the imaging
vessel and the excitation light is projected on just that bottom part of
the vessel, it is possible to reduce background light and thereby improve
the contrast of the images obtained.
As a means that can be used to ensure that just the bottom portion of the
vessel is illuminated, a cover can be positioned to prevent the upper part
of the imaging vessel from being illuminated by the excitation light, or
the same effect can be obtained by using a cover with a slit-shaped
aperture.
In such a case, the fluorescent particles can be illuminated even more
effectively by using a cylindrical lens or the like to convert the thin
excitation laser beam into a wide, flat beam in order to illuminate just
the bottom portion of the vessel. The same effect can also be obtained by
deflecting the excitation light along the bottom portion, or by projecting
the excitation light via a bundle of optical fibers the exit end of which
is arranged in a straight line.
Thus markedly reducing the amount of background light allows the
fluorescent particles to be imaged with high contrast, thereby increasing
the reliability of the fluorescent particle count.
Further features of the invention, its nature and various advantages will
become more apparent from the accompanying drawings and following detailed
description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing the general configuration of an apparatus
for imaging fluorescent particles according to the present invention.
FIG. 2 is a front view of the apparatus used for analyzing and displaying
obtained fluorescent particle images.
FIG. 3 is a diagram illustrating an arrangement of a cover used to shield
the upper part of the imaging vessel.
FIG. 4 is a diagram illustrating another arrangement for shielding the
upper part of the imaging vessel from illuminating light.
FIG. 5 is a diagram of an optical system used to form a strip-shaped
excitation light beam.
FIG. 6 is a diagram of another optical system used to form a strip-shaped
excitation light beam.
FIG. 7 is a diagram showing the configuration of optical elements used to
form a strip-shaped excitation light beam.
FIG. 8a is an exterior perspective view of the imaging vessel.
FIG. 8b is a cross-sectional view of the vessel.
FIG. 8c is a bottom view of the vessel.
FIG. 9 is a cross-sectional horizontal view of an imaging vessel according
to another configuration.
FIG. 10 is a cross-sectional view of an imaging vessel according to yet
another configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 and 2 show the arrangement of a first embodiment of the present
invention. In the drawings, reference numeral 1 denotes a laser light
source, such as, for example, a YAG laser that produces a green laser
beam. The laser beam from the laser light source 1 impinges upon, and is
diffused by, a diffusion plate 2 comprised of ground glass or other such
member that is able to diffuse light. The light thus diffused is projected
at a bottom section or portion 3' of an imaging vessel 3, which has a
generally tubular body the upper section or part 25 of which is covered by
a cover 4. The bottom portion 3' has a side wall 27 and a bottom wall 28.
Fluorescent particles are accumulated in an interior space 26 at the
bottom portion of the imaging vessel 3, and these fluorescent particles
fluoresce when illuminated by the laser beam. The images of the
fluorescent particles illuminated by the laser beam pass via a cover-glass
5 and objective lens 6 to a mirror 7 that reflects the images to a barrier
filter 8 that transmits light in a prescribed frequency band, and are then
picked up by a CCD camera 9.
The images of the fluorescent particles picked up by the CCD camera 9 are
passed via a signal line 10 to a video capture device 11 of a computer 12,
where they are processed by an image processing circuit 13 (FIG. 2) to
enable the fluorescent particles to be recognized. There is a change in
brightness where there is a fluorescent particle, so the fluorescent
particles can be recognized by, for example, using the differentiation of
signal values to detect the positional coordinates of the particles. The
fluorescent particles thus recognized are displayed on a monitor 14. FIG.
2 depicts the image 15 of the bottom portion of the vessel together with a
plurality of fluorescent particles 15a therein, displayed on the monitor
14. The fluorescent particles 15a are counted and the count is also
displayed at the lower part 16 of the monitor 14.
The imaging vessel 3 is molded in one piece from transparent polystyrene
resin, glass, or acrylic resin, preferably polystyrene resin. Inserted
into the imaging vessel 3 are a platelet preparation sample (100
microliters, for example), a chemical (Triton X) that dissolves platelet
and leukocyte cytoplasm, and a fluorescent dye (propidium iodide) for
staining leukocyte nuclei. The imaging vessel 3 is then subjected to
centrifugal separation in a centrifuge (not shown), causing the leukocyte
nuclei to collect in the bottom portion of the imaging vessel 3. All of
the leukocyte nuclei can be collected in the bottom portion 3' of the
imaging vessel 3 by applying a prescribed centrifugal force.
The cover 4 is then used to cover the imaging vessel 3 in which the
leukocyte nuclei stained with a fluorescent dye are collected in the
bottom portion 3' thereof, and the imaging vessel 3 is mounted on the
imaging apparatus. For imaging, the laser light source 1 is activated,
producing a laser beam which is diffused by the diffusion plate 2 and
projected onto the bottom portion 3' of the imaging vessel 3. As the
nuclei of the leukocytes in the bottom portion 3' of the imaging vessel 3
have been stained with a fluorescent dye, when they are illuminated by the
beam of excitation light, they emit fluorescent light having a frequency
of around 600 nm. This is picked up via the cover-glass 5, objective lens
6, mirror 7 and barrier filter 8 below the imaging vessel 3. The barrier
filter 8 only transmits light having the frequency of fluorescent light,
allowing light of harmful frequencies to be blocked at this point.
The laser beam is projected only at the bottom portion of the vessel,
effectively illuminating the leukocytes collected there. Therefore, even
if there is fluorescent dye floating in the solution in the imaging vessel
3, it is possible to prevent the fluorescent dye from forming harmful
background light, thereby enabling the images to be obtained with improved
contrast.
With reference to FIG. 2, the images of fluorescent particles thus obtained
by the CCD camera 9 are passed via a signal line 10 to a video capture
device 11 of a computer 12, where they are processed by an image
processing circuit 13 to count the number of leukocytes 15a.
In accordance with the arrangement described above, the laser beam is
projected only onto the bottom portion of the imaging vessel and does not
illuminate the upper part of the vessel. As shown by FIG. 3, the effect of
only illuminating the bottom portion can be enhanced by providing a cover
20 that shields all parts other than the bottom portion from the
illuminating light beam.
Instead of the cover arrangement of FIG. 3, an arrangement such as that
shown in FIG. 4 may be used. In this arrangement, a mask 21 having a
central slit-shaped aperture 21a is used. The laser beam from the laser
light source 1 passes through the aperture 21a, ensuring that only the
bottom portion 3' of the imaging vessel 3 is illuminated.
A linear or line-shaped light beam would illuminate more of the bottom
portion of the imaging vessel than a spot-shaped beam. FIG. 5 shows the
type of arrangement that could be used in such a case, with laser beam 30
being shaped to a flat beam 33 by passage through cylindrical lenses 31
and 32, and the flat beam 33 being used to illuminate the bottom portion
3' of the imaging vessel 3 by projecting the flat beam 33 in a direction
generally parallel to the bottom wall 28 of the bottom portion 3'.
FIG. 6 shows another arrangement, in which a scanning mirror 40 is used to
deflect the laser beam 30, which passes through a lens 41 to scan the
bottom portion of the imaging vessel.
FIG. 7 shows another arrangement, that uses a bundle of optical fibers. In
this arrangement, the fibers at the entrance end 50 from which the laser
beam enters are arranged in a round configuration, while at the exit end
51 the fibers are arranged in a straight line, with the exit end 51 being
disposed in the vicinity of the bottom portion of the imaging vessel so as
to illuminate the bottom portion thereof.
In each of these embodiments, only the bottom portion of the vessel, or the
vicinity thereof, is illuminated, by a strip-shaped beam, thereby making
it possible to obtain images of the fluorescent particles with good
contrast. Moreover, if a diffusion plate 2 is used to diffuse the laser
beam, it enables the bottom portion of the imaging vessel to be
illuminated uniformly.
FIG. 8 shows a preferred embodiment of the imaging vessel 3, preferably
formed as a one-piece molding of polystyrene resin. The vessel has a
ringshaped upper portion 3a having a notch 3f for positioning purposes.
The imaging vessel 3 comprises a cylindrical portion 3b that extends
vertically downward from the upper portion 3a to a small-diameter portion
3d, via a sloping portion 3c. A substantially square or rectangular block
portion 3e is formed at the lower end. One side of the block portion 3e is
arranged to be illuminated by a laser beam, indicated by the arrow. When
fluorescent particles are to be imaged, the imaging vessel 3 is attached
to the apparatus, with the notch 3f being used to position the imaging
vessel 3. When the vessel 3 has been fitted into position, a flat face of
the block portion 3e is perpendicular to the direction of laser beam
illumination, forming the entry surface for the incident beam. Thus, the
laser beam illuminates only the bottom portion 3g of the imaging vessel 3.
The bottom portion m ay also be illuminated by an arrangement such as the
one shown in FIG. 9, in which the block portion 3e has a round
cross-section, and a negative cylindrical lens 60 is disposed on the side
from which the bottom portion is illuminated by the excitation beam.
In the arrangement shown in FIG. 10, a cover 70 is used to shield parts of
the imaging vessel 3 other than the bottom portion from the laser beam. In
this case, the cover 20, shown in FIG. 3, on the imaging apparatus side
may be omitted. The cover or shielding function may be realized by
applying a light shield coating to the vessel, or by painting the vessel
in a shielding color.
It is to be understood that while in the foregoing the invention has been
described with reference to leukocytes as the fluorescent particles, the
invention is not limited thereto but can be applied to other fluorescent
particles.
As described in the foregoing, in accordance with the present invention,
fluorescent particles to be imaged are collected in the bottom portion of
an imaging vessel, only that bottom portion is illuminated by an
excitation light beam, and the bottom portion is imaged from below. The
result is that background light is reduced, making it possible to obtain
high-contrast images of the fluorescent particles, thereby making it
possible to evaluate the images of the fluorescent particles and count
them with greater precision.
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